WOMS
P code powertrain Medium severity

P20C1 Reductant Heater "C" Control Circuit/Open

The OBD2 code P20C1 indicates a malfunction in the control circuit for the reductant heater "C," which is responsible for heating the diesel exhaust fluid (DEF) to ensure proper operation.

Definition

The OBD2 code P20C1 indicates a malfunction in the control circuit for the reductant heater "C," which is responsible for heating the diesel exhaust fluid (DEF) to ensure proper operation. The "Open" part of the code suggests a break or fault in the electrical circuit, preventing the heater from functioning correctly

Common causes

  • Faulty reductant heater "C"
  • Open or shorted wiring in the control circuit
  • Bad connector or corroded terminals
  • Failed power supply to the heater
  • Malfunctioning engine control module (ECM)
  • Blown fuse related to the reductant heater circuit

Common misdiagnoses

  • Faulty reductant heater
  • Open or shorted wiring in the circuit
  • Defective engine control module (ECM)
  • Issues with the reductant pump
  • Faulty temperature sensor
  • Problems with the exhaust aftertreatment system
  • Incorrectly diagnosed fuel system issues
  • Battery or charging system problems

Troubleshooting steps

  1. 1. Check for Additional Codes

    Use an OBD-II scanner to check for any other related trouble codes. This can provide more context and help identify if there are multiple issues

  2. 2. Inspect Wiring and Connectors

    Visually inspect the wiring and connectors associated with the reductant heater "C". Look for signs of damage, corrosion, loose connections, or frayed wires. Repair or replace any damaged components

  3. 3. Test the Reductant Heater

    If accessible, test the resistance of the reductant heater "C" using a multimeter. Compare the readings to the manufacturer's specifications. If the resistance is out of range, the heater may be faulty and need replacement

  4. 4. Check the Control Circuit

    Inspect the control circuit for continuity. Use a multimeter to check for open circuits or shorts in the wiring. Ensure that the circuit is properly grounded

  5. 5. Examine the Power Supply

    Verify that the reductant heater is receiving the correct voltage. Check the power supply to the heater and ensure that it is within the specified range

  6. 6. Inspect the Engine Control Module (ECM)

    The ECM controls the operation of the reductant heater. Check for any software updates or known issues with the ECM. In some cases, reprogramming or replacing the ECM may be necessary

  7. 7. Check for Environmental Factors

    Ensure that there are no environmental factors affecting the operation of the reductant heater, such as extreme temperatures or contamination

  8. 8. Clear the Codes and Test Drive

    After performing repairs, clear the trouble codes using the OBD-II scanner and take the vehicle for a test drive to see if the code returns

  9. 9. Consult Technical Service Bulletins (TSBs)

    Check for any TSBs related to the P20C1 code for your specific vehicle make and model. Manufacturers may have issued guidance or fixes for known issues

  10. 10. Seek Professional Help

    If the issue persists after performing these steps, it may be necessary to consult a professional mechanic or technician who has experience with diesel exhaust systems and OBD-II diagnostics. By following these troubleshooting steps, you can systematically identify and resolve the issue associated with the P20C1 code